Finland has the European Union’s longest border with Russia at 1,300 kilometers (800 miles), while Sweden’s island of Gotland is in a strategically important location in the Baltic Sea, not far from the Russian exclave of Kaliningrad. Four Russian combat aircraft violated Swedish airspace east of Gotland on Wednesday, coinciding with a military exercise by Swedish and Finnish forces around the island.

In the last week, Finnish politicians have held a raft of meetings to discuss how to respond to Russia’s aggression against its neighbor, and on Friday, the nation’s president, Sauli Niinisto, will visit President Joe Biden in Washington, D.C.

In a survey commissioned by Swedish tabloid Aftonbladet, 51% of respondents said they think Sweden should join the North Atlantic Treaty Organization, with 27% opposed. The poll shows a clear shift from January, when 42% backed Swedish membership in the alliance.